[116.01] An Observational Test for Water Ice at the Mercurian Poles

R. Killen (SwRI)

The poles of Mercury have been shown to be highly reflective in the radar and this was attributed to the presence of water ice. The presence of OH above the poles is shown to be an observational test of polar ice deposits. We have calculated the OH column which should be observed for various assumed temperatures and morphologies of the ice deposit. We show the predicted column for surface temperatures from 95 to 130 K and for pure ice under 1 cm of dust and for an ice/dust layer, respectively. The amount of water which is degassed is not highly sensitive to whether the ice is mixed with dust or is pure ice under a dust layer. The amount of water and OH in the exosphere depends on both temperature and time since emplacement. We discuss constraints on the possible accretion of water to the poles.